On many online websites, registered and/or unregistered users (referred to as “Users”) can, among other things, create accounts, play games, and communicate with each other. Messages (referred to as “Content”) can be sent between Users, or to the internet population in general, through an internal or external email system, an instant messaging system, message boards, chat rooms, or any other method of displaying Content to other Users. Content sent by some Users may be inappropriate for the purpose of the website or otherwise in violation of the policies established by the website owner or sponsor for its Users. This is especially true for websites geared towards children. The present invention filters Content sent by Users that contains undesirable words or phrases, and can either block the Content from being viewed or replace the Content with language acceptable to the website owner or sponsor.